Refactor to enforce strictNullChecks

This commit applies `strictNullChecks` to the entire codebase to improve
maintainability and type safety. Key changes include:

- Remove some explicit null-checks where unnecessary.
- Add necessary null-checks.
- Refactor static factory functions for a more functional approach.
- Improve some test names and contexts for better debugging.
- Add unit tests for any additional logic introduced.
- Refactor `createPositionFromRegexFullMatch` to its own function as the
  logic is reused.
- Prefer `find` prefix on functions that may return `undefined` and
  `get` prefix for those that always return a value.

src/infrastructure/Events/EventSubscriptionCollection.ts

@@ -9,12 +9,9 @@ export class EventSubscriptionCollection implements IEventSubscriptionCollection
   }
 
   public register(subscriptions: IEventSubscription[]) {
-    if (!subscriptions || subscriptions.length === 0) {
+    if (subscriptions.length === 0) {
       throw new Error('missing subscriptions');
     }
-    if (subscriptions.some((subscription) => !subscription)) {
-      throw new Error('missing subscription in list');
-    }
     this.subscriptions.push(...subscriptions);
   }